Okay...so I am a bit puzzled here. I have an Evo IX with an Intake, HPF3.5" exhaust, dynoflash tune, fuel pump, and boost controller. I am running 20psi. THe car has 17k miles, and lately it has been bucking really hard in the lower gears at full throttle.

I thought that the stock plug gap might be too big, but I closed it up and that did not help. I tried going to a Denso IKH24 plug, and that did not help either. I have closed that gap all the way to .023 and the car still falls on its face at full throttle.

I really thought it was an ignition issue, but I am lost. Any ideas would be great!

 

Explain the problem in more detail. What rpm...which gears...what psi...pre-boost...mid-boost...after boost...? When did it start? What exactly do you mean by bucking?

 

[QUOTE=snake679]Okay...so I am a bit puzzled here. I have an Evo IX with an Intake, HPF3.5" exhaust, dynoflash tune, fuel pump, and boost controller. I am running 20psi. THe car has 17k miles, and lately it has been bucking really hard in the lower gears at full throttle. [/QUOTE]

What intake are you running? Does it only buck in the lower gears and runs fine in 4th & 5th, then? Is this a mail-in flash? Stock DV? Was the fuel pump installed with the install kit, or just the pump itself? Have you run any leaded gas through it? What boost controller, manual or electronic?

 

It seems to be doing it in lower gears..1-3. It usually occurs mid to upper boost levels at 4-6k rpm. By bucking...it stalls, and falls on it's face, then picks back up. It is fairly violent.

It is a forge MBC, and it is the stock DV. The flash is a mail in dynoflash tune.

The fuel pump was installed without a kit, however I did install a brand new fuel pump outlet 0-ring from the dealer at the time of install.

The plugs were very normal looking when I pulled them out, so I did not think that it was a fuel supply problem, but I could be wrong. Could the DV be opening?

 

Nothing but 92 octane has been run through the car.

 

Hah, you said lower rpm earlier. Lower rpm means like 1-3k rpm. 4-6k rpm with a violent "buck" sounds like fuel cut or blowing off an IC pipe under boost, but your flash should have removed fuel cut, and if an IC pipe was dislodging itself under boost, you'd probably hear it.

This is not related to the DV, and it does not make sense that it would happen in lower gears as opposed to higher gears.

 

I said lower gears, but none the less..

So you think this is a fuel issue?

 

boost leak.

 

I have been scouring for boost leaks, and have not been able to find anything....I was pretty sure that was the problem at first...but no luck finding anything.

 

no CEL? sounds like the problem I'm having although it's not very frequent. Does this happen more with partial throttle acceleration (no matter what gear you're in) or does it happen closer to WOT? (By partial throttle, i mean you're cruising along and barely step on the gas to accelerate)

 

ok im haveing a problem simular to that i just put a little intake on my evo 8 and it feels like its lost a substantual amount of power since adding the intake. all my car has done is a blow off valve and the intake... i wounder why its doing this??..... not getting enough fuel maybe.?.?.?
or maybe i need to turn up boost but i dont see turning up boost helping my problem.. another thing is the car has idel droop and in higher rpms i am also having the car cut out and then come back on strang........ some one please help!!!!!!

 

Intakes will just screw up your A/F ratio making it run rich.
Same with an atmospheric vented BOV reciculating BOV's shouldn't have this issue.
Tuning for these parts take care of the power loss.


EDIT:
I forgot to mention, since your messing with the airflow on the MAF its possible its getting erractic readings, thus the bucking.

 

you should have bought some different mods

 

Could be vapor lock in your fuel, or bad gas, i.e. water/crap in gas. Run it empty and refuel with 92+ at a station you know is good - pay that extra .10 if you have to.

You said you did a boost leak test? No hissing?

Strange question (I think way outside the box) - are your battery connections tight? If you have a loose connection that could explain bucking - car wants to turn off. Just throwing that out there.


EvOVIIIJaY -- Wow, you shouldnt be modding your car. Like said earlier - intake bad. You need to be tuned for that. And VTA BOV...that idle drop is you ECU saying "WTF, thanks for making me run like crap".

 

Ot never happens at less than 90% throttle.....


And I will double check the battery connections....